It is known today for a wireless mobile station, such as a cell phone, to be able to gain telephone connectivity via a WLAN (e.g., 802.11) access point. To provide such connectivity, the access point can be connected with a packet-switched network, and a media gateway system can then be provided as an interface between the packet-switched network and a traditional telephone system such as the public switched telephone network (PSTN). The mobile station can then place and receive telephone calls via a communication path comprising (i) an air interface connection with the access point, (ii) the packet-switched network, (iii) the media gateway system, and (iv) the PSTN or other telephony system.
In typical practice, the mobile station will associate with the access point through an open association process or through use of a secure key process such as WEP or EAP for instance. Once associated, the mobile station will then acquire an IP address from the access point, so that the mobile station can engage in packet-data communication via the access point. The mobile station will then register with the media gateway system, via the access point and packet-switched network. And in response, the media gateway system, functioning as the equivalent of a legacy mobile switching center (MSC), will send a registration notification message to the mobile station's home location register (HLR), to establish that the media gateway system is now serving the mobile station. The mobile station may then place and receive PSTN calls via the access point and media gateway system.
By way of example, once the mobile station associates with the access point and acquires an IP address, the mobile station may send to the media gateway system a Session Initiation Protocol (SIP) REGISTER message specifying the mobile station's telephone number in the “From” field or other SIP header. In response, the media gateway system may dip into an authentication server (e.g., a RADIUS server) to authenticate the mobile station and may then send an IS-41 Registration Notification (REGNOT) message via a signaling network to the mobile station's HLR to indicate that the media gateway system is serving the mobile station. Upon receipt of a registration notification return result (regnot_rr) message from the HLR, the media gateway system may then respond with a SIP 200 OK to the mobile station to confirm successful registration.
Thereafter, to place a PSTN call, the mobile station may send to the media gateway system a SIP INVITE specifying the called number, and the media gateway system may responsively engage in legacy ISUP signaling to set up the call via the PSTN to that number. After further signaling, a packet-based call leg may thus be set up between the mobile station and the media gateway system and a circuit-based call leg may be set up between the media gateway system and the called party, and the media gateway may bridge those legs together to allow the call to proceed.
Similarly, when a PSTN call is placed to the mobile station's telephone number, ISUP signaling may pass to the media gateway system (as the mobile station's serving “switch”), and the media gateway system may responsively engage in SIP signaling with the mobile station, to set up the call via the packet-switched network to the mobile station. After further signaling, a circuit-based call leg may be set up between the calling party and the media gateway system and a packet-based call leg may be set up between the media gateway system and the mobile station, and the media gateway system may bridge the legs together to allow the call to proceed.
With this arrangement, a mobile station that is equipped to engage in WLAN communication can conveniently associate with an access point (provided the mobile station can meet any necessary security procedures, such as WEP for instance), and the mobile station can then place and receive calls just as though the mobile station were communicating via a traditional cellular telephone network.